Republican Scott Baugh, a former state assemblyman, reportedly started the process of filing for the House race Wednesday, but has additional steps to take before California’s filing deadline on Friday.

With nine Democrats looking to unseat Rohrabacher, Democrats fear the large field could split the party’s vote in the June 5 primary and lead to Rohrabacher and another Republican making the ballot in November.

Democrats are worried that they could get shut out of several top California House races because of crowded primaries. California has a top-two primary system, which sees candidates face off in an all-party primary before the top two vote-getters advance to a general election runoff.

Baugh raised $576,000 ahead of the 2016 election, according to Federal Election Commission filings. But he previously told reporters that he’d only run if Rohrabacher retired.

Rohrabacher has served in Congress for nearly three decades, but he faces his toughest reelection race to date. Clinton won the Orange County district by a little over a point, while Rohrabacher won reelection by 17 points.

Rohrabacher, a member on the House Foreign Affairs Committee, is considered one of the most pro-Russia members of Congress, which could become a hindrance in his 2018 campaign.